class_docstr: Gym Dictionary with arbitrary keys updatable after instantiation
  
  Example:
     space = FlexDict({})
     space['key'] = spaces.Box(4,)
  See also: documentation for gym.spaces.Dict
code: def __setitem__(self, key, space):
      self.assertSpace(space)
      self.spaces[key] = space
  
file_path: ray/rllib/utils/spaces/flexdict.py
imports: import gymnasium
  from ray.rllib.utils.annotations import PublicAPI
label_desc: Use image node_id 5 for calling the FlexDict obj's underlying member method code with example usage: obj.__setitem__(key, space) without return types